In the ink-jet recording process, small droplets of an ink composition are ejected and attached to a recording medium, such as paper, to effect printing. According to innovative progress of ink-jet recording techniques in recent years, the ink-jet recording process is being used in the field of high definition printing, which has been realized only by silver salt photography and offset printing. In view of the trend, such an ink-jet recording medium is developed that has high gloss equivalent to photographic paper and coated paper used in the field of silver salt photography and offset printing.
As an ink for recording a character and/or an image on the ink-jet recording medium having high gloss, an aqueous ink is ordinarily used which contains water as a major component with a colorant, a resin and other various additives added thereto. While the colorant may be a dye or a pigment, a pigment is favorably used from the standpoint of weather resistance, such as light resistance, gas resistance, water resistance and humidity resistance. Accordingly, the demand of a pigment ink is being increased, and development thereof is promoted to utilize the advantages of pigments. In order to improve the fixing property of the pigment and the gloss on a recording medium, an aqueous pigment ink containing a resin component has been used (as described, for example, in Patent Documents 1 and 2).
Upon forming a recorded image with high gloss with an aqueous ink containing a resin component, a recorded image ink layer on the surface of the recording medium is produced from a pigment layer and formed thereon a sole resin layer containing only a resin, so as to realize high gloss. For example, as shown in FIG. 2, an aqueous pigment ink is ejected to a surface of a recording medium 1, and after the solvent component penetrates through the interior of the recording medium 1, an ink layer 10 as a recorded image is formed on the surface of the recording medium 1. In the interior of the ink layer 10, the pigment particles 21 are accumulated in the closest packing state to from a pigment layer 2. The resin component contained in the aqueous pigment ink fills up the gaps among the pigment particles 21 in the pigment layer 2, and the entire pigment layer 2 is completely covered with a resin 31 to form a sole resin layer 3 containing substantially no pigment particle on the pigment layer 2. Furthermore, the surface 4 of the sole resin layer 3 can be extremely smooth to realize high gloss.
Patent Document 1: Japanese Patent No. 3,088,588
Patent Document 2: WO 03/097753
The recorded image shown in FIG. 2 can realize gloss with high quality, but the inventors have found that upon irradiating the image with strong light from a short distance, the image includes such problems that uncomfortable feeling is formed due to strong glare, and thin film interference is formed by the sole resin layer. For example, in the case where the recorded image shown in FIG. 2 is irradiated with illumination of a naked light bulb or naked fluorescent light, a clear mirror image of the naked light bulb or naked fluorescent light is formed on the surface 4 of the ink layer 4, and its strong reflected light causes an observer with uncomfortable feeling. The ink layer 10 shown in FIG. 2 has a multilayer structure containing the pigment layer 2 and the sole resin layer 3 to form thin film interference by the sole resin layer 3, and thus the reflected light is separated into weak components and strong components depending on wavelength, which brings about incorrectness in color reproducibility.